ANSYS Fluent 2024 R1 – Combustion is not sustaining despite high ignition temperature (DRM19 CHEMKIN)
Hi everyone,
I'm simulating methane-air combustion in ANSYS Fluent 2024 R1 using a CHEMKIN DRM19 reduced mechanism (Finite Rate chemistry with Species Transport).
My main issue is that the combustion never sustains.
To initiate ignition, I created a high-temperature ignition region near the methane injector and tried temperatures between 2000 K and 3000 K. Despite this, the flame extinguishes after a short distance instead of becoming self-sustaining.
The resulting temperature field stays around 250–300 K throughout most of the domain, whereas I would expect combustion temperatures of approximately 2000–3000 K. The contours clearly show that the hot region disappears and no stable flame develops.
So far I have tried:
- Importing the DRM19 CHEMKIN mechanism.
- Different under-relaxation factors.
- First- and second-order discretization schemes.
- Different pressure-velocity coupling methods (SIMPLE and Coupled).
- Different methane/oxygen flow conditions, including stoichiometric oxygen.
- Running for more than 1000–5000 iterations.
However, the result is always the same: ignition does not sustain and the domain cools back to near ambient temperature.
My question is:
What are the most common reasons why a methane flame fails to sustain in Fluent despite initializing an ignition zone at 2000–3000 K?
Could this be due to:
- Incorrect inlet conditions or mixture fraction?
- Residence time being too short?
- Turbulence-chemistry interaction?
- CHEMKIN mechanism import/settings?
- Heat losses to the walls?
- Something else that I'm overlooking?
I'd appreciate any suggestions from anyone who has successfully simulated methane combustion with DRM19 or other detailed chemistry mechanisms in Fluent.